Potassium and Magnesium Supplementation Do Not Protect Against Atrial Fibrillation After Cardiac Operation: A Time-Matched Analysis

Abstract

Introduction Despite a lack of demonstrated efficacy, potassium and magnesium supplementation are commonly thought to prevent postoperative atrial fibrillation (POAF) after cardiac surgery. Our aim was to evaluate the natural time course of electrolyte level changes after cardiac surgery and their relationship to POAF occurrence. Methods Data were reviewed from 2041 adult patients without preoperative AF who underwent CABG and/or valve surgery between 2009 and 2013. In patients with postoperative AF, the plasma potassium and magnesium levels nearest to the first AF onset time were compared to time-matched electrolyte levels in patients without AF. Results POAF occurred in 752 patients (36.8%). At the time of AF onset or the matched time point, patients with POAF had higher potassium (4.30 vs. 4.21 mmol/L, p<0.001) and magnesium (2.33 vs. 2.16 mg/dL, p<0.001) levels than controls. A stepwise increase in AF risk occurred with increasing potassium or magnesium quintile (p<0.001). On multivariate logistic regression analysis, magnesium level was an independent predictor of POAF (OR 4.26, p<0.001), in addition to age, Caucasian race, preoperative beta blocker use, valve surgery, and postoperative pneumonia. Prophylactic potassium supplementation did not reduce the POAF rate (37 vs. 37%, p=0.813), while magnesium supplementation was associated with increased POAF (47 vs. 36%, p=0.005). Conclusion Higher serum potassium and magnesium levels were associated with increased risk for POAF after cardiac surgery. Potassium supplementation was not protective against POAF, while magnesium supplementation was even associated with increased POAF risk. These findings help explain the poor efficacy of electrolyte supplementation in POAF prophylaxis.

Serum Electrolyte Concentrations and Their Association With Postoperative Atrial Fibrillation: A Long-Standing Myth or Reality?

“…A similar observational study was published by Lancaster et al in the Annals of Thoracic Surgery in 2016, including data from 2,041 patients without preoperative AF who underwent coronary artery bypass grafting or valve surgery. 15 Similar to Howitt et al, the authors found that serum K + and Mg ++ concentrations were largely within the normal range postoperatively, and severe deficiencies were rare. In addition, in a time-matched analysis, serum K + and Mg ++ concentrations were found to be higher in patients with POAF compared with those without (mean serum K + concentrations 4.3 v 4.21 mmol/L and serum Mg ++ concentrations, 2.33 v 2.26 mg/dL, respectively, both p < 0.001), albeit by a small margin.…”

Morbidity and mortality with atrial fibrillation following colorectal surgery

“…Hypokalaemia alters the resting membrane potential and the configuration of the action potential. Hypomagnesaemia interferes with Na‐K ATPase pump function and calcium handling, intensifying the pro‐arrhythmic affect of hypokalaemia . There is a discrepancy in the literature with several studies showing hypomagnesaemia and hypokalaemia has an association with POAF, however Lancaster et al .…”

“…Hypomagnesaemia interferes with Na-K ATPase pump function and calcium handling, intensifying the pro-arrhythmic affect of hypokalaemia. 20,21 There is a discrepancy in the literature with several studies showing hypomagnesaemia and hypokalaemia has an association with POAF, 6,7 however Lancaster et al has shown with time matched analysis, prophylactic potassium supplementation had no protective effect and magnesium supplementation is associated with an increased risk of POAF. Similarly, the postoperative magnesium was statistically significantly higher in the POAF group compared with the controls (1.06 versus 0.83).…”

Magnesium and Cardiovascular Disease

“…Similarly, two other metaanalyses of magnesium administration in the prevention of AF after cardiac surgery reported different outcomes (92,93). Moreover, a recent time-matched analysis study advised against prophylatic magnesium supplementation as higher magnesium levels increased the risk of postoperative AF (94). As such, there are currently no firm recommendations for the use of magnesium to prevent arrhythmia post AMI and cardiac surgery.…”